twin disc conversion

[Ewan 500 K1]

worth putting some posts in "desperately seeking"  ... if you do go with two wheel spares my experience is that they will go with a lower "offer" on ebay than their stated starting price.
If getting a second hand caliper you probably  want to budget for new piston and seal ... as well as being wary of the bleed nipple issue oddjob points out. DSS has a compete caliper with piston seal, pads etc for £118

[Johnwebley]

thanks for your helpful advice,Ewan and Oddjob

I have got the caliper and bracket,pipes and mastercylinder,(ex CB550) ,looks far better condition,and cheaper,

Oddjob,if you have a disc,please let me know,

we can work a deal ,

deciding on which forks to buy,the scruffy,or the bright blue ??

thanks

John

[Ewan 500 K1]

I've got 3 sets of forks .. one set for cafe, one for the basket case and one spare. I was hoping that I'd go out an measure the bottom half sliders/cover hoping they'd all be the same ... they're not !

Set 1, off a 500K1 I think. this set only allows a single disc and have gaiters. The covers are 315mm long from centre of axle hole to top of cover
The covers have the following marking just above the axle seat:
Left cover,  on one side: 5 (and barely legible: 2726)   &   on the other side: HF  5
Right cover,   same markings as right hand side.

If we knew for certain which covers are interchangeable between which models we could maybe extend your choice and look at condition of covers only on the basis that this would be all you need if you can determine which are interchangeablle with your own ...by referring to the number markings on your own fork covers ?

[Ewan 500 K1]

Set 2, this set allow for dual discs & has gaiters. Again the covers are 315mm long from centre of axle hole to top of cover. This set are marked "341" half way up the lower cover , so presumably off a 750 or 550. According to motogrid the covers are common to the 550 and 750, part numbers 51521-341-701 (left) and 51421-341-01 (right). None of the other sets are stamped half way up the covers.
The covers have the following marking just above the axle seat:
Left cover,  on one side: L1  5  + some very lightly stamped imperceptibe text  &   on the other side: HF  5 + some japanese characters
Right cover, on one side: 55Y 14R  &   on the other side 5  HF + some japanese characters
.... cover possibly interchageable with set 1, above .. (what I think is a 500K1 set) given that covers are same lenght and are all marked HF 5

[Ewan 500 K1]

Set 3 , pretty sure that these are off a 550K3. Have no gaiters and covers are 350mm long from centre of axle hole to top of cover. These are the ones on my cafe build
The covers have the following marking just above the axle seat:
Left cover,  on one side: L   4   (L party gone)   &   on the other side: 3    P
Right cover, on one side: R    5  &   on the other side:  4    Q

[matthewmosse]

I do recall that the k3 lowers on my k3s were longer than my 500(74 vintage) for some reason though the 500 still has dual disk capacity but no trace of fittment ever being carried out. I'm not sure the the 550f followed the 500 or the k3 pattern and I'd suspect mix and match could end up being a headache in terms of parts being different. I have a few spare sets of forks but not where I can get at them easily. Nor could I say what bike they were off as I've tended to buy when the price made sence in the knowledge that stuff breaks eventually - My first 550 - the brake mounts just decided to crumble - I think some chemical influence or frost plus corrosion but the mount just looked cracked and when I tried to undo the bolt the mount turned to dust 

[Bryanj]

I think that its only the K3 that is different, can't remember what 550 i got my other slider off but it was from a breaker in about 78 so i am pretty sure it was not K3 as they did not have new write off bikes.

Again NONE of the 500 that were offical honda imports to UK had a second caliper mounts as they were all officially K1 models

[Ewan 500 K1]

.  Don't even remember buying them, weird.

... I'd take the 0.5 overs off you if you're interested in disposing of them oddjob

[Ewan 500 K1]

I think that its only the K3 that is different, can't remember what 550 i got my other slider off but it was from a breaker in about 78 so i am pretty sure it was not K3 as they did not have new write off bikes.

Again NONE of the 500 that were offical honda imports to UK had a second caliper mounts as they were all officially K1 models

Was there a 500K3 ? .. I've a 500K3 / 550K3 original parts book . In this both models use the same forks that allow for dual discs . Maybe the 500K3 never got imported to UK ?

[Bryanj]

500K3 was european mainland only and never officially came to UK, But have seen a couple in the last few years

[matthewmosse]

I've had 2 cb550k3's the first was known to me and my mates as 'box of cogs' as that was how it arrived. I learnt a fair bit re assembling the rusty pile of scrap into a workable machine - it came with 2 engines - one the camchain tensioner had let go and the gearbox was full of metal that had scored all the selector groves and forks - the other engine wasn't much better, I bought a 3rd that was so rotten the cluch casing had litrally turned to oxide  and only bits were left and the entire thing was full of mud but the top end was perfect under the thick mud. It unsurprisingly seized it's crank on the first outing - was a bit on the rough side) That bike had a sticker from a dealer in 'little leaver' Bolton on the sidepannel both were T reg and I had them over 10 years ago. I sold the frame of the other after it snapped a camshaft - it was my first big bike after passing my test and was £220 including 6 months tax and test and had all the chromework appart from the front mudguard painted gold   It did however thrash my mates superdream on economy on motorways and match it penny for penny on A roads and was armchair comfortable.

[Ewan 500 K1]

( John .. sorry for the thread hijack , but got prbs with PM sanding at times  ! )
Odjob , I've PM'd you re 0.5 oversizes)

[Johnwebley]

ok,update coming,

forks arrived,they must have been for a 550k,so the slider was the same length as my 500.,
think the internals are different,but I am expecting to just fit on my existing stanchion,and use same springs and internals,

disc ordered,

and caliper,bracket hoses,etc

I intend to use a double length banjo to join the brake pipes,so I don't need to worry  about brakelight switch,

hopefully the new bolts,and speedo drive mods will go OK

[Yoshi823]

I fitted twin discs to my commuter 550F1 & they made the world of differance. I also drilled the discs & used a set of Vesrah pads on one side & Ferodo pads in the other caliper. This was so that, in the rain it would act like a single disc but in the dry like twin discs. I used a standard 550F2 master cylinder with Aeroquip lines feeding to both calipers directly from the splitter under the headlight.

Sorry I can't post up any pics atm but photobucket say I need to upgrade my account as i've used all of my bandwidth this month 

[Johnwebley]

starting to get all the bits together,

cleaning and checking


 ordered new master cylinder ,and various seal ,

servicing caliper,

HINT !!
a broken piston ring is perfect for cleaning the seal groove in the caliper !!!!!

more posts as I go along